The subject matter herein relates generally to signal transmission electrical cables and shielding efficiency for signal conductors.
Shielded electrical cables are used in high-speed data transmission applications in which electromagnetic interference (EMI) and/or radio frequency interference (RFI) are concerns. Electrical signals routed through shielded cables radiate less EMI/RFI emissions to the external environment than electrical signals routed through non-shielded cables. In addition, the electrical signals being transmitted through the shielded cables are better protected against interference from environmental sources of EMI/RFI than signals through non-shielded cables.
Shielded electrical cables are typically provided with a cable shield formed by a tape wrapped around the conductor assembly. Signal conductors are typically arranged in pairs conveying differential signals. The signal conductors are surrounded by an insulator and the cable shield is wrapped around the insulator. However, manufacturing tolerances of the conductors and the insulator can lead to performance degradation in high speed signal cables. For example, differences in the diameters of the conductors leads to performance degradation in the form of electrical signal timing skew. It is desirable to have diameters of the conductors closely matched. Current manufacturers of drawn copper conductors have a manufacturing tolerance of +/−5 micrometers or microns (approximately 0.0002″). This amount of variation in the copper conductors drives signal integrity failures at high speeds resulting in marginal performance and increased scrap.
A need remains for an electrical cable that improves signal performance.